Apparatus for the automatic startup of a continuous casting line

ABSTRACT

An apparatus for the automatic startup of a continuous casting line, including a vessel which is connected to a tip by means of a gate, the tip feeding a casting housing. The apparatus includes a laser device which measures the level of the metal within the vessel, a level control device, which adjusts the introduction of liquid metal into the vessel, a gate actuator to control the gate for providing a barrier between the vessel and the tip, a transducer for the temperature of the metal inside the vessel, and a PLC which receives data from the temperature transducer and from the laser device to control the level control device and the gate actuator, so as to adjust the vessel metal level to ensure a correct and continuous flow of metal toward the casting cylinders, to avoid poor diffusion of the metal inside the tip.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation in part of application Ser. No.15/483,363 filed Apr. 10, 2017 and claims the priority of Italian PatentApplication No. UA2016A002539 (corresponding to No. 1020160000 37889),filed on 13 April 2016, the subject matter of which applications isincorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to an apparatus for the automatic startupof a continuous casting line, particularly for the production ofaluminum or zinc strips.

More particularly, the invention relates to a system installed in acaster for controlling the flow of metal with which the tip of thecaster is fed.

Conventionally, the startup of a continuous casting machine is acompletely manual operation effected by the operator, the person incharge of the caster line, until the standard production conditions arereached, which include:

1) metal level;

2) strip thickness;

3) line speed;

4) roller lubrication;

5) temperature of casting roller cooling water.

The startup of the continuous casting (caster), as well as control ofthe metal level, is a critical step in the operation of the system.

The startup is in fact a very delicate operation that determines thefinal quality of the product.

The entire operation is entrusted to the management of the line on thepart of the operator, who, depending on his experience, might performthe operation more or less appropriately.

The duration of a startup is around 15-20 minutes and the operations tobe performed are numerous and must be performed in a timely andsequential manner, considering the duration of the event, which islimited.

The startup of a continuous casting for aluminum or zinc consists inmaking liquid metal flow by means of casting channels, passing through avessel known as a head box, which has a barrier at the end in order toprevent the access of the liquid metal to the inside of the tip whilewaiting for the required metal temperature to be reached (for aluminumapproximately 735° C. and 470° C. for zinc), the metal is conveyed intothe collection vessels (ladles).

Once the required temperature has been reached, the operator throttlesthe flow of metal by means of the level control (actuator), using themanual closing/opening controls that are present on the control post.

At this point the operator visually checks that the metal level that ispresent in the head box reaches the required level.

Once the level height has been reached, the operator prepares forremoval of the manual barrier (monolith plate) arranged in the end ofthe head box, making the liquid metal converge toward the inlet of thetip; in this operation, which lasts approximately 20-30 seconds, theoperator must pay maximum attention to correctly dosing the quantity ofmetal, then he must adjust the flow constantly and precisely, assistedby the commands of the operators who wait for the solid strip at theoutput of the caster (on the front part of is the cylinders), until thetip is completely filled.

Once the colleagues upstream of the line, who are waiting for thesolidification of the strip, have given clearance, the operator who isperforming the starting operation must adjust the level by means of aflow regulator (actuator) by means of the manual controls (open/closebutton).

During the adjustment step, the operator controls the level detected bythe laser that is present above the head box.

Once the level has stabilized, the operator engages the automatic metallevel adjustment control by pressing the “automatic level” button.

This function provides for the flow regulator (actuator) to enter asymbiosis with the laser, giving rise to an automatic adjustment, usingthe latter as feedback for the closure of the PID adjustment loop.

During casting it is necessary to complete the rest of the operations,which are:

power-on of the spraying system (graphite);

power-on of the cylinder cooling water pump.

These two operations are manually controlled by the operator.

The spraying system is fundamental in order to avoid the adhesion of thealuminum strip on the casting cylinders; graphite performs the role ofrelease agent and also is fundamental in the first minutes of casting;an excessive or insufficient quantity would compromise the continuationof casting.

The power-on of the water pump avoids an overheating of the jacket ofthe steel roller, usually the water must be activated after reaching thesurface temperature of the jacket, not before 200° C. in order to avoidthermal shocks to the steel, thus the operator must perform manualcontrol, after ascertaining the temperature of the jacket he can proceedwith flushing of the cooling water.

OBJECTS OF THE INVENTION

The aim of the present invention is to improve the prior art.

Within the scope of this aim, an object of the invention is to providean apparatus which, in a continuous casting line, or caster, allows toperform the appropriate automatic adjustments in relation to the workingconditions required to start the line automatically.

Another object of the present invention is to provide a reliable andsafe apparatus.

SUMMARY OF THE INVENTION

This aim and these objects and others which will become better apparenthereinafter are achieved by an apparatus for the automatic starting of acontinuous casting line.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages will become better apparent fromthe description of preferred but not exclusive embodiments of theinvention, illustrated by way of nonlimiting example in the accompanyingdrawings, wherein:

FIG. 1 is side view of the apparatus for the automatic starting of acontinuous casting line, according to the present invention;

FIG. 2 is a side view of a continuous casting line, for the productionof aluminum or zinc strips, provided with the automatic startingapparatus according to the present invention;

FIG. 3 is a top plan view of the apparatus;

FIG. 4 is a side view of the water feeding system;

FIG. 5 is a side view, opposite to the preceding one, of the waterfeeding system;

FIG. 6 shows the start up page of the control software;

FIG. 7 shows the save page of the control software.

DETAILED DESCRIPTION

With reference to the cited figures, the automatic starting apparatusaccording to the invention, globally designated by the reference numeral1, is inserted in a continuous casting line for the production ofaluminum or zinc strips, known as caster, which is shown schematicallyin FIG. 2.

The apparatus 1 according to the present invention is installed in thecaster to control the flow of metal with which the nozzle, or tip, 2 isfed.

The tip 2 distributes the molten metal in a casting housing which isconstituted by two casting rollers 3 and 4, which are water-cooled bymeans of a spraying system 5, where the molten metal is cooled andsolidified to form a strip 6.

The water is provided by means of a water feeding system which includes:

an upper roller water intake, having a temperature control thermocouple20, a flow control valve 23, and a pressure control valve 25,

a lower roller water intake having a temperature control thermocouple21, a flow control valve 24, and a pressure control valve 26,

an upper roller water outlet having a pressure control valve 27, and atemperature control thermocouple 29,

a lower roller water outlet having a pressure control valve 28 and atemperature control thermocouple 30.

The molten metal flows in a channel 8, until it reaches a vessel 9,known as head box, which reaches the tip 2.

Ducts 15 connect the vessel 9 to molten metal collection trays 16, 17,18.

The strip 6 then passes through a series of apparatuses which includeshears 10 and a winding spool 11.

According to the present invention, the apparatus, includes a laserdevice 12 for controlling the level of the metal inside the vessel 9, alevel control device 7, which adjusts the introduction of the liquidmetal in the vessel 9 and a gate actuator 13 for the control of the gatefor providing a barrier between the vessel and the mouth of the tip.

The apparatus also has a temperature transducer, constituted by athermocouple 14, for controlling the temperature of the metal in thevessel 9, and a PLC management unit with a corresponding operator panel.

The operation of the automatic control apparatus according to thepresent invention is as follows.

Initially, the molten metal is made to flow into the vessel 9, the endof which is blocked by the refractory barrier, i.e., the gate, which isnot visible in the figures, connected to the motorized systemconstituted by the gate actuator 13, until the required parameters arereached.

Once the start temperature, measured by means of the thermocouple 14,has been reached, the electronic control system sends a command to thelevel control device 7, which reaches a set closure position, waiting toreach the preset level, through the drain channel, which is calibrateddepending on the thickness of the strip, on the widths and on thealloys.

The level of the metal, previously established by a set point, isfurther confirmed by means of a reading performed by the laser device12, which actuates the gate actuator 13 so that the motorized refractorybarrier opens gradually and progressively, according to a positioningprofile stored previously on a work recipe.

The gate actuator is operated by a gear train having zero play connectedto a brushless motor with feedback position control.

Once the filling of the tip 2 has been completed, the level of the metalin the vessel 9 is adjusted by means of an automatic system, in order toensure a correct and continuous flow of metal toward the casting rollers3 and 4.

During the entire starting step, the level control device 7,communicating with the laser device 12, maintains the previously enteredset point, i.e. the optimum casting level.

Once the casting strip has formed, the automatic control system adjuststhree other fundamental parameters: the speed of the rollers 3 and 4,the cooling water dispensed by the spraying system 5, and the releaseagent 5 on the cylinders.

Description of Software Management And Operation

FIG. 6 shows the screen page that allows to perform automatic startup ofthe line according to a previously recorded sequence; it also allows torecord a startup sequence by performing the startup operations manuallyand acquiring all the main parameters that are significant for linestartup until start has occurred.

Automatic. Startup Sequence

The procedure for automatic line startup can be performed from theoperator panel and its various steps can be monitored from the samepanel. After choosing a previously recorded file (work recipe) andloading it in the “Load/Save Rec Files” page, it is possible to:

start the sequence

monitor the state of advancement of the preliminary steps

monitor the advancement of the execution of the recorded file.

STEP1: The first step of the automatic startup sequence consists influxing the molten metal inside the channels 15 toward the collectiontrays 16, 17 and 18; this step is performed with the gate fully closedand the level adjustment actuator fully open; in this step, thetemperature of the metal bath is monitored with the thermocouple 14.

Cast Temp: When this temperature is higher than the Tresh Temp, theprocedure moves on to the next step.

Cast Temp: Display field in which the measured temperature of the metalbath is monitored.

Tresh Temp: Input field in which it is possible to set the thresholdtemperature for moving on to the next step of the sequence.

STEP2: The second step of the automatic startup sequence consists inwaiting for the metal to continue to flux and keep its temperatureconstant for a specified time. If the temperature drops below therequired value (Tresh Temp) during this wait time, the procedure returnsto STEP 1.

Wait time: Display field in which the elapsing of the pause time ismonitored.

Set time: Input field in which it is possible to set the pause timeduring which the metal must continue fluxing at the requiredtemperature.

STEP3: The third step of the automatic startup sequence consists inclosing the metal level, adjustment actuator 7 to a position that can bepreset, so as to empty the bath to the point of interrupting the fluxingof the metal; when the actuator reaches the preset position, theprocedure moves on to the next step.

Act Pos: Display field in which the position reached by the actuator ismonitored so as to check the progress of the action;

Set Pos: Input field in which it is possible to set the position of theactuator for adjusting the level of metal to be reached.

STEP4: The fourth step of the automatic startup sequence consists inwaiting for the level of the metal bath to drop below a preset level,which must be lower than the level of the bath fluxing drain channels;as soon as the level of the metal drops below the preset level, theprocedure moves on to the next step;

Met. Lev.: Display field in which the level of the metal measured by thelaser sensor is monitored.

Set Lev.: Input field in which it is possible to set the level to bereached in order to be able to move on to the next step.

STEP5: In the fifth step of the automatic startup sequence, the systemstarts reading the values of the main parameters that are significantfor the line startup sequence, stored previously in a file, and usesthem as set points of the line in the current startup step.

The parameters are sampled and recorded with a predefined interrupt timeduring recording, and likewise the samples are read and performed withthe same interrupt time during execution, so as to faithfully repeat theentire startup process performed previously.

The main parameter that is reproduced is the position of the gate, whichis opened in steps by reproducing exactly the maneuvers performed by theoperator in the sampled sequence performed manually; at the same time,the system sets to automatic mode the metal level adjustment andtherefore the actuator is actuated so that the level remains at thevalue set in the “Set Met Lev” field in the “Step 5” row. In this way,the system opens the gate gradually, causing the gradual lowering of thelevel of the metal, and this in turn causes the gradual opening of themetal level adjustment actuator in order to keep this level constant atthe set value.

During sampling steps (work cycle recordings), the following lineparameters are also monitored and recorded:

1) Roller speed 3 and 4

2) Casting roller cooling temperature

3) Upper and lower roller water flow-rate

4) Roller release agent translation speed and start 5

which are reproduced exactly in the startup step.

The management and correct holding of the water flow-rate andtemperature at the casting rollers (present in the recipe) are ensuredby the software management that the control unit (PLC) performs with theaid of the data that it receives from the thermocouples, flow controlvalves and pressure control valves, listed hereinafter:

Upper roller water intake temperature control thermocouple 20

1) Upper roller water outlet temperature control thermocouple 29;

2) Lower roller water intake temperature control thermocouple 21;

3) Lower roller water outlet temperature control thermocouple 30;

4) Upper roller water flow control valve 23;

5) Lower roller water flow control valve 24;

6) Upper roller water intake pressure control valve 25;

7) Upper roller water outlet pressure control valve 27;

8) Lower roller water intake pressure control valve 26;

9) Lower roller water outlet pressure control valve 28;

Sample in esecuz: Display field in which the sample number currentlybeing executed in the startup sequence is displayed; the increment ofthis field allows to check the correct progress of the execution of thesequence.

Precond: This button allows to set the preconditions required tocommence automatic startup; these preconditions are full closure of thegate (position=0) and level adjustment actuator open to at least 40%. Ifthese conditions are met, the button becomes green and it is thereforepossible to start the automatic startup sequence without pressing thebutton again.

START: This button allows to start the automatic startup sequence of theline;

STOP: This button allows to stop the automatic startup sequence of theline, returning the file execution index to the beginning.

RECORD STARTUP SEQUENCE: In the yellow box it is possible to store asequence for the automatic startup of the line that has occurred with apositive outcome: it is necessary to execute the sequence manually,recording the main parameters in memory with an interrupt-basedsampling, and once it has been verified that the startup has had apositive outcome it is necessary to decide to save the stored data in afile chosen at will or to delete the data.

During the manual sequence it is necessary to perform the entire fluxingstep while the gate is fully closed and the actuator is fully openwithout starting the recording; at the end of the fluxing step theactuator is closed almost completely (it is usually left 3%-5% open inorder to ensure a minimal passage of the metal) and the level of themetal decreases until the level of the drains is reached: this step,too, is not recorded; at this point it is necessary to click the “STARTREC” button, which will be stored without starting the recording;recording will actually start when the gate first leaves the fullyclosed position (height equal to 0 mm) and will last until the “STOPREC” button is clicked.

START REC: This button allows to start the startup data recordingsequence; the button must be pressed after performing manually all thesteps for fluxing, closure of the actuator with consequent levelreduction, just before the opening of the gate; the pressing of thebutton will be recorded and the recording will begin only when the gatemoves from the fully closed position.

STOP REC: This button allows to stop the data recording sequence.

Automatic Startup Parameters

The lower part of the screen displays all the main parameters that areimportant in the execution of startup; they are:

Metal level

Actuator position

Gate position

Roller speed

Casting roller cooling water temperature

Two values on two superimposed rows are presented for each one of theseparameters:

SP—This is the value set by the system as adjustment set point, which isset manually when in the recording step or taken from the recording fileor from the settings of steps 1-5 when in the step of execution of anautomatic startup.

PV—This is the value measured by the system in real time, so that it ispossible to appreciate any differences with respect to the set value.

Load/Save Recording File

FIG. 7 shows the page that allows to save in mass storage the recordingof a previously performed automatic startup or to load from mass storagea previously saved startup file that can be executed again.

When a startup sequence is recorded, its file remains in memory, readyto be saved in mass storage, until a new recording is made or the PLC isswitched off; this means that a startup sequence performed manually withsuccess and recorded can be saved to mass storage even several daysafter its recording and can also be saved multiple times in differentpaths or with different names until a new manual sequence is recorded.

Likewise, when a startup sequence is loaded from mass storage and isready to be executed automatically, it remains in memory and can beexecuted again several times until a new file is loaded from massstorage or until the PLC is switched off.

Moreover, one should bear in mind that the recorded sequences to besaved in mass storage and the ones loaded from mass storage to beexecuted occupy separate memory spaces and therefore, loading a newsequence from mass storage does not overwrite the manually recordedsequence and likewise the recording of a new sequence performed manuallydoes not overwrite the last sequence loaded from mass storage.

For the same reason, a recorded manual startup sequence, in order to beexecuted automatically, must be first saved in mass storage, andtherefore must be reloaded from mass storage.

SAVE FILE

Browse: This button allows to open a pop-up dialog box which allows toselect the directory where the startup file with the stored data is tobe saved; the default directory in which the file is stored is in the“Recipes” directory; in this directory it is possible to create furthersubdirectories or delete them or move files from one subdirectory toanother, so as to create a customized file organization; however, onemust bear in mind that it is necessary to choose a path before savingthe file, otherwise the file will not be saved; the selected path mustbe confirmed with the “OK” button: pressing this button closes thedirectory selection pop-up dialog box and displays the selected path inthe alphanumeric output field located directly to the right of the“Browse” button; to exit from the pop-up dialog box without making anyselection, consequently confirming the previously saved path (if one hasalready been chosen), press the “CANCEL” button, which closes theselection pop-up dialog box without performing any action.

New File Name: This is an alphanumeric input/output field in which it ispossible to enter the name to be given to the recording file; the nameentered here must not have a suffix, since the system will automaticallyadd the “.CSV” suffix to the file name; moreover, the system willconcatenate the file name entered here with the path selected in the“BROWSE” field in order to obtain the complete path of the file to berecorded.

Save: This button allows to write all the data recorded during the laststartup sequence to a file chosen at will on a mass storage mediumconnected to the controller; before starting the writing process it isnecessary to select a valid directory and enter a valid file name. Thestored file is a normal text file, with the “.CSV” extension, with theindividual fields separated by “;” and the individual records separatedby “NEW LINE” characters; therefore, the recorded files can be read andedited easily with any text editor (for example Notepad.exe) and can beimported into any spreadsheet (for example Microsoft Excel) thatsupports the “.CSV” format; in this manner it is possible to eliminateand/or edit any parts of the sequence that do not meet processrequirements. It is also possible to provide a graphical representationof the variables.

Writing Recipe Record: This display field shows the number of the samplebeing written during the step for writing to file the stored data; inthis manner it is possible to monitor the progress of the writingprocess and check, at the end of this process, how many samples form thefile.

LOAD FILE

Browse: This button allows to open a pop-up dialog box, with which it ispossible to select the directory from which the startup file to beexecuted with the stored data is to be loaded; the default directoryfrom which the file is stored is in the mass storage of the PLC in the“Recipes” directory, where it is possible to create additionalsubdirectories or delete them or move files from one subdirectory to theother, so as to create a customized file organization; once the desiredpath has been selected, it is necessary to select the file that oneintends to read and the selection must be confirmed by means of the.“OK” button: pressing this button closes the directory selection pop-updialog box and displays the path, complete with the file name selectedin the alphanumeric output field located directly to the right of the“Browse” button; to exit from the pop-up dialog box without performingany selection and accordingly confirming the previously saved file nameand path (if already chosen), press the “CANCEL” button, which willclose the selection pop-up dialog box without taking any action.

Load: This button allows to read all the recorded data from the selectedfile; before starting the reading process, it is necessary to select avalid directory and a valid file name from the ones proposed in theselection pop-up dialog box.

Reading Recipe Record: This is a display field which shows the number ofthe sample being read during the step for transferring the data of thefile into system memory; in this manner it is possible to monitor theadvancement of the reading process and, at its end, check how manysamples form the file.

It has been found in practice that the invention has achieved theintended aim and objects, providing an apparatus for the automatic startof a continuous casting line that allows to obtain some importantadvantages with respect to traditional systems.

The present apparatus ensures an increase in startups performedsuccessfully and a decrease in the waste of consumables (tip, end darn,fiber).

The apparatus according to the present invention furthermore offers anincrease in productivity due to the higher percentage of startupscompleted successfully.

The apparatus according to the invention is susceptible of numerousmodifications and variations, all of which are within the scope of theinventive concept; all the details may furthermore be replaced withtechnically equivalent elements.

The materials used, as well as the dimensions, may of course be anyaccording to the requirements and the state of the art.

1-8. (canceled)
 9. An apparatus in a continuous casting line,comprising: a vessel; a tip connected to said vessel and defining anoutlet, said tip feeding a casting housing, said casting housingcomprising casting rollers; a spraying system configured to water-coolsaid casting rollers; a water feeding system feeding water to saidspraying system, said water feeding system comprising at least one waterintake having a temperature control thermocouple, a flow control valve,and a pressure control valve, at least one water outlet having apressure control valve, and a temperature control thermocouple; a gateat said outlet, providing a movable or adjustable barrier between thevessel and the tip; a laser device which measures the level of the metalwithin said vessel; ducts connecting said vessel to molten metalcollection trays; a level control device, which adjusts the introductionof liquid metal into said vessel; a gate actuator operatively connectedto said gate to control said gate, said gate actuator being operated bya gear train connected to a brush less motor with feedback positioncontrol; a transducer for sensing temperature of metal inside saidvessel; and an electronic management unit operatively connected to saidtransducer and said laser device and configured to carry out anautomatic startup process including (a) holding said gate in a closedposition during a startup phase, (b) once a predetermined starttemperature of liquid metal in said vessel has been attained, asmeasured by said transducer, sending a command to said level controldevice to reach a set closure position, and (c) once a predetermined setpoint in the level of liquid metal in said vessel has been attained, asdetermined by readings of said laser device, operating said gateactuator to open said gate gradually and progressively in accordancewith a stored positioning profile, said electronic management unit beingfurther configured to carry out a continuous state process includingcontrolling said level control device and said gate actuator to adjustthe level of said metal in said vessel in order to ensure a correct andcontinuous flow of metal toward said casting housing, said electronicmanagement unit being further configured to adjust the speed of saidrollers and the cooling water dispensed by said spraying system.
 10. Theapparatus according to claim 9, wherein said casting housing comprisestwo casting rollers, said water feeding system comprising: an upperroller water intake having a temperature control thermocouple, a flowcontrol valve, and a pressure control valve; a lower roller water intakehaving a temperature control thermocouple, a flow control valve, and apressure control valve; an upper roller water outlet having a pressurecontrol valve and a temperature control thermocouple; and a lower rollerwater outlet having a pressure control valve and a temperature controlthermocouple.
 11. The apparatus according to claim 9, wherein saidelectronic management unit comprises a programmable logic controller(PLC).
 12. The apparatus according to claim 9, wherein said transducercomprises a thermocouple.
 13. The apparatus according to claim 9,wherein said gate comprises a refractory barrier.
 14. A method for anautomatic startup of a continuous casting line, wherein said continuouscasting line comprises: a vessel; a tip connected to said vessel anddefining an outlet, said tip feeding a casting housing, said castinghousing comprising casting rollers; a spraying system configured towater-cool said casting rollers; a water feeding system feeding water tosaid spraying system, said water feeding system comprising (i) at leastone water intake having a temperature control thermocouple, a flowcontrol valve, and a pressure control valve, and (ii) at least one wateroutlet having a pressure control valve, and a temperature controlthermocouple; a gate at said outlet, providing a movable or adjustablebarrier between the vessel and the tip; a laser device which measuresthe level of the metal within said vessel; ducts connecting said vesselto molten metal collection trays; a level control device, which adjuststhe introduction of liquid metal into said vessel; a gate actuatoroperatively connected to said gate to control said gate, said gateactuator being operated by a gear train connected to a brushless motorwith feedback position control; a transducer for sensing temperature ofmetal inside said vessel; and an electronic management unit operativelyconnected to said transducer and said laser device and configured tocarry out an automatic startup process; said method comprising: (a)holding said gate in a closed position during a startup phase, (b) oncea predetermined start temperature of liquid metal in said vessel hasbeen attained, as measured by said transducer, sending a command to saidlevel control device to reach a set closure position, and (c) once apredetermined set point in the level of liquid metal in said vessel hasbeen attained, as determined by readings of said laser device, operatingsaid gate actuator to open said gate gradually and progressively inaccordance with a stored positioning profile, and further configured tocarry out a continuous state process including controlling said levelcontrol device and said gate actuator to adjust the level of said metalin said vessel in order to ensure a correct and continuous flow of metaltoward said casting housing; operating said electronic management unitto adjust the speed of said rollers and the cooling water dispensed bysaid spraying system.
 15. The method according to claim 14, furthercomprising: step 1—with said gate fully closed and the level controldevice fully open, flowing molten metal inside said channels to saidcollection trays and monitoring a temperature of a metal bath; step2—upon the temperature of the metal bath rising above a thresholdtemperature, waiting for the metal to continue to flow and keeping itstemperature constant for a specified time, and upon the temperature ofthe metal bath dropping below the threshold temperature during thewaiting, further performing the flowing and monitoring of step 1; step3—closing said level control device to a preset position, so as to emptythe bath to the point of interrupting the flowing of the molten metal;step 4—upon said level control device reaching the preset position,waiting for the level of the metal bath to drop below a preset level,which must be lower than the level of the bath fluxing drain channels;step 5—upon the level of the metal dropping below the preset level,reading the values of the main parameters that are significant for theline startup sequence, stored previously in a file, and using saidparameters as set points of the line in the current startup step, saidparameters being sampled and recorded with a predefined interrupt timeduring recording, said samples being read and performed with the sameinterrupt time during execution, so as to faithfully repeat a previouslyperformed startup process, one of said main parameters that isreproduced being the position of the gate, which is opened in steps byreproducing exactly the maneuvers performed by an operator in a sampledsequence performed manually; at the same time, setting to automatic modesaid level control device for metal level adjustment and actuating saidlevel control device so that the level of molten metal remains at avalue set in step 5; opening the gate gradually, causing a graduallowering of the level of the metal, and causing a gradual opening of thelevel control device in order to keep this level constant at the setvalue.
 16. The method according to claim 15, comprising, during thesampling steps, monitoring and recording the following line parameters:roller speed, roller cooling temperature, upper and lower roller waterflow-rate, roller release agent translation speed and start.